It is very important to design smaller boats with flotation devices in the hull to ensure that the boat remains floating in case substantial water gets into the boat or the boat capsizes. Additionally, foam flotation devices provide the boat with added buoyancy, thus increasing carrying capacity and safety. The installation of foam flotation devices is especially important in the case of small boats which are designed for operation on rough waters, such as in the case of rescue boats.
Many prior art boat designs incorporate foam devices within the hull of the boat, as in U.S. Pat. No. 4,060,865 (Woolworth). Typically, the foam flotation members are incorporated directly within the hull structure itself. These boat designs are generally safer than designs which do not incorporate flotation devices within the hull. Prior art designs use foam flotation devices within the hull to increase safety but do not take full advantage of the unique properties of the foam flotation devices in order to increase boat performance.
In U.S. Pat. No. 4,287,624 (Lowther), a series of foam flotation devices or wings are attached to the exterior and interior of a low-speed fishing boat. The exterior wings extend from the transom approximately to the point halfway between the transom and the bow where the wings terminate, thus presenting a large flat surface to the oncoming waves. The foam flotation wings provide increased stability and buoyancy to the boat hull, however, the teachings of Lowther would create significant problems if used on a high-performance, high-speed power boat. The flat surface presented to the water by the termination of the foam flotation wing would create a substantial hazard if the boat was operated at speeds over simple trolling speeds. At high speeds, the flat surface of the flotation wings could cause a loss of control of the boat or could cause the boat to "trip" on a wave, possibly capsizing the boat.
In the context of a boat, "tripping" means that an exterior surface of the boat contacts the water creating a force which causes the boat to deviate from its intended path. As an example, if the flat surface of the flotation wings in Lowther were to contact the water when the boat was moving at high speed, the force produced by the water striking the flat surface could cause the boat to begin spinning or even to list to the extent that the boat capsizes.
In addition to the problems described above, the method used to attach the flotation devices to the boat hull also creates a number of disadvantages. In Lowther, the flotation wings are attached by bolting through the foam wings and boat hull. This creates a number of holes in the hull and thus a significant risk of water leakage. If a boat incorporating the teachings of Lowther were operated at high speeds, the significant water pressures would likely force the foam flotation devices away from the hull, possibly resulting in loss of control of the boat or damage to the hull and the foam flotation devices. The water pressure would also likely force water through the holes by means of which the foam flotation devices are attached to the hull.
Other prior art boat designs use inflatable cylinders to form the sides of the boat, as in the case of Zodiac boats. The inflatable cylinders provide a high degree of stability to the boat but result in a loss of performance. Generally, prior art inflatable boat designs use inflatable cylinders as the sides of the boat and either a flexible floorboard or a rigid floorboard formed of wood or fiberglass. In operation, the cylinders serve as the running surface for the boat and remain in contact with the surface of the water; thus, a substantial wetted surface area and a significant amount of drag are created. This design also results in a very poor ride due to the fact that the boat tends to skip or bounce over the top of the waves. In addition, the inflatable cylinders are easily damaged and must constantly be inspected for tears, leaks, etc. Another disadvantage to inflatable boats is that typically the interior of the boat is very small, thus leaving little room for carrying equipment or passengers.